bugfix: fast scroll flickering (#226)

android/build.gradle

@@ -25,7 +25,7 @@ android {
 dependencies {
     implementation fileTree(include: ['*.jar'], dir: 'libs')
     implementation 'com.facebook.react:react-native:+'
-   implementation 'com.henninghall.android:NumberPickerView:1.1.4'
+    implementation 'com.henninghall.android:NumberPickerView:1.1.5'
     implementation 'org.apache.commons:commons-lang3:3.7'
     implementation group: 'net.time4j', name: 'time4j-android', version: '4.2-2018i'
 }

android/src/main/java/com/henninghall/date_picker/pickers/AndroidNative.java

@@ -13,9 +13,13 @@ import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 
+import static android.widget.NumberPicker.OnScrollListener.SCROLL_STATE_FLING;
+import static android.widget.NumberPicker.OnScrollListener.SCROLL_STATE_IDLE;
+
 public class AndroidNative extends NumberPicker implements Picker {
 
     private Picker.OnValueChangeListener onValueChangedListener;
+    private int state = SCROLL_STATE_IDLE;
 
     public AndroidNative(Context context) {
         super(context);
@@ -87,6 +91,11 @@ public class AndroidNative extends NumberPicker implements Picker {
         // Not needed for this picker
     }
 
+    @Override
+    public boolean isSpinning() {
+        return state == SCROLL_STATE_FLING;
+    }
+
     @Override
     public void smoothScrollToValue(final int value) {
         final AndroidNative self = this;
@@ -176,11 +185,9 @@ public class AndroidNative extends NumberPicker implements Picker {
     public void setOnValueChangedListener(final Picker.OnValueChangeListener listener) {
         this.onValueChangedListener = listener;
         super.setOnScrollListener(new OnScrollListener() {
-            int previousState = SCROLL_STATE_IDLE;
-
             @Override
-            public void onScrollStateChange(NumberPicker numberPicker, int state) {
-                boolean stoppedScrolling = previousState != SCROLL_STATE_IDLE && state == SCROLL_STATE_IDLE;
+            public void onScrollStateChange(NumberPicker numberPicker, int nextState) {
+                boolean stoppedScrolling = state != SCROLL_STATE_IDLE && nextState == SCROLL_STATE_IDLE;
                 if (stoppedScrolling) {
                     new Handler().postDelayed(new Runnable() {
                         @Override
@@ -190,7 +197,7 @@ public class AndroidNative extends NumberPicker implements Picker {
                         // the delay make sure the wheel has stopped before sending the value change event
                     }, 500);
                 }
-                previousState = state;
+                state = nextState;
             }
         });
     }

android/src/main/java/com/henninghall/date_picker/pickers/IosClone.java

@@ -44,4 +44,9 @@ public class IosClone extends NumberPickerView implements Picker {
     public View getView() {
         return this;
     }
+
+    @Override
+    public boolean isSpinning() {
+        return super.isScrolling();
+    }
 }

android/src/main/java/com/henninghall/date_picker/pickers/Picker.java

@@ -24,6 +24,7 @@ public interface Picker {
     void setWrapSelectorWheel(boolean wrapSelectorWheel);
     void setDividerHeight(int height);
     void setItemPaddingHorizontal(int padding);
+    boolean isSpinning();
 
     interface OnValueChangeListenerInScrolling {
         void onValueChangeInScrolling(Picker picker, int oldVal, int newVal);

android/src/main/java/com/henninghall/date_picker/ui/WheelChangeListenerImpl.java

@@ -32,6 +32,8 @@ public class WheelChangeListenerImpl implements WheelChangeListener {
 
     @Override
     public void onChange(Wheel picker) {
+        if(wheels.hasSpinningWheel()) return;
+
         WritableMap event = Arguments.createMap();
         TimeZone timeZone = state.getTimeZone();
         SimpleDateFormat dateFormat = uiManager.getDateFormat();

android/src/main/java/com/henninghall/date_picker/ui/Wheels.java

@@ -180,4 +180,10 @@ public class Wheels {
         }};
     }
 
+    public boolean hasSpinningWheel() {
+        for(Wheel wheel: getAll()) {
+            if(wheel.picker.isSpinning()) return true;
+        }
+        return false;
+    }
 }